A portable apparatus, having a slide mechanism by which an upper casing can be made to slide with respect to a lower casing, comprises: an assist mechanism, disposed between the upper casing and the lower casing, and assisting sliding of the upper casing. The assist mechanism comprises: a first support member attached pivotably to the upper casing or to a member fixed to the upper casing; a second support member attached pivotably to the lower casing or to a member fixed to the lower casing; at least one first elastic spring biasing the first support member; at least one second elastic spring biasing the second support member; and a holding case that holds the first and second elastic springs in a serially arrayed state with a direction of extension and contraction of the first elastic spring forming a prescribed angle to that of the second elastic spring, the first support member being slidably inserted in the direction of the first elastic spring, and the second support member being slidably inserted in the direction of the second elastic spring.